Hey guys i'm new here and i come from the mn12 universe. I just bought a 1994 Ultra with 159k miles on it for 2k. Car is VERY clean inside and out and it runs great!. The only thing that concerns me is the tensioner that runs on the sc and waterpump belt is going out, where can I find one? The arm is jumping around alittle. The sc is also making some rattling noises inside I think it may be from the coupler or something. How hard is it to rebuild/replace the sc and how much is it? The noise goes away when you drive it but then when at idle or at alight you can hear it. I've noticed that when the tensior stops moving so much the noise in the sc kinda quiets down. Plus the gasket between the sc and the lower is leaking but outside of that this car is great shape. Any comments and suggestions appreciated, thank you.

Congrats on the purchase -those Park Ave Ultra'* are some of the smoothest riding cars ever from any of the 'Big 3'.
Your best bet for the tensioner is to check your local salvage yards, but chances are a used one will probably go bad soon after replacement. Otherwise the best alternative is to just get a new one.

For the SC coupler check ebay or just about any of the 3800 aftermarket suppliers (www.intense-racing.com, www.zzperformance.com, www.3800performance.com) and on ebay do a search with the key words: "Eaton Coupler", "SSEi Coupler", "M62" or "M90 coupler".
Should cost around $70 IIRC for the gaskets, SC oil (use only GM SC oil from your local dealer or sellers on ebay), and a coupler.

Good luck and welcome to the club.